Power bank



FIG. 1 is a perspective view of a power bank;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is a side view thereof;

FIG. 6 is a back view thereof; and,

FIG. 7 is a front view thereof. 

CLAIM The ornamental design for a power bank, as shown and described. 